From: Rick DeNatale <rick.denatale@...>
Date: 2009-03-30T20:56:26+09:00
Subject: Re: Symbols garbage collector in Ruby1.9, fixed?

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On Mon, Mar 30, 2009 at 4:09 AM, I=F1aki Baz Castillo <ibc@aliax.net> wrote=
:

> Hi, in Ruby 1.8 there is an issue when adding more and more Symbols
> since they remain in memory and are never removed.
>
> I'm doing a server in Ruby that receives messages with headers (From,
> To, Subject, X-Custom-Header-1...) and after parsing I store the
> headers in a hash using symbols as keys:
>
>  headers =3D {
>    :from =3D> "alice@aaa.com",
>    :to =3D> "bob@bbb.com",
>    :"x-custom-header-1" =3D> "Hi there"
>  }
>
> I could use strings as keys instead of symbols, but I've checked that
> getting a Hash entry is ~25% faster using Symbols.
>
> The problem is that I could receive custom headers so for each one a
> new Symbol would be created. An attacker could send lots of custom
> headers to fill the server memory and cause a denial of service.
>

Which is why Rails (actually activesupport) which implements a
HashWithIndifferentAccess to allows using strings and symbols equivalently
for hash access, uses the string form in the actual hash forgoing the acces=
s
performance in favor of safety.


--=20
Rick DeNatale

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